The present invention relates to a barrier rib forming method for a gas discharge display panel utilizing a gas discharge, and more particularly, to a barrier rib forming method for a gas discharge display panel which is made to form the barrier rib in a state wherein a photoresistor remains on the surface of an anode upon manufacturing a matrix type gas discharge display panel.
In general, a gas discharge display panel is a displaying element in which an inert gas is introduced and sealed between the upper and lower separate electrodes formed respectively on each surface of two glass substrates, and wherein displaying numerals, letters and the like is accomplished by utilizing the gas discharge produced upon applying a voltage at the electrodes having a structure that, as shown in FIG. 1, includes a cathode group Y composed of electrodes y.sub.1 -y.sub.n with predetermined distance intervals therebetween formed on the surface of a glass substrate 1a located at the rear side as viewed in the displaying direction, and an anode group X composed of electrodes x.sub.1 -x.sub.n with predetermined distance intervals therebetween formed on the glass substrate 1b located at the front side, and barrier ribs 2 made from glass paste formed between the anodes x.sub.1 -x.sub.n within a structure that said two glass substrates 1a and 1b confronting one another.
The gas discharge display panel having such structure as aforementioned is usually provided with the operational potentials in sequential time sharing to each electrode y.sub.1 -y.sub.n of the cathode group Y, while the operational potentials corresponding to the display signals are applied sequentially or simultaneously to each electrode x.sub.1 -x.sub.n of the anode group X of the opposite side, so that a display picture can be obtained in line sequence or point sequence by discharging between each electrode x.sub.1 -x.sub.n, y.sub.1 -y.sub.n in response to the magnitude of the potential difference corresponding to the display signals.
At this moment, in order to restrain the diffusion of plasma glow generated at the cathode, the barrier ribs are usually formed by printing on the glass substrate formed with the anode or the glass substrate formed with the cathode.
Japanese laid open patent application Sho-58-150248, which is a prior art of the gas discharge display panel having such electrode structure, describes that the insulation barrier ribs are of a predetermined height for the prevention of the plasma glow (becoming the factor of error during display) generated at the cathode and are formed by the screen printing method so as to direct from the surface of a substrate provided with the anode group X toward the cathode group Y.
The conventional barrier rib forming method according to the above-described usual screen printing method will be described in detail with reference to the process sequence diagrams shown in FIG. 2 as follows.
Here, the forming of the barrier ribs is a process of forming the electrode, in which at first ITO(Indium Thin Oxide) film 5 is coated on the surface of the glass substrate 1 in order to form the anode, and photoresist 6 is coated on said ITO film 5 by using a spin coater or the like and then being dried, and thereafter the photoresist 6 is exposed by utilizing a photo mask of predetermined pattern and being developed.
And thereafter, when it is processed by ITO etching solution, the non-hardened portion of the photoresist 6 and the portion of the ITO film 5 corresponding thereto are removed. Accordingly only the photoresist 6 of the hardened portion and the portion of the ITO film 5 corresponding thereto remain on the glass substrate 1.
When the glass substrate 1 in such condition is processed with a photoresist removing solution, the remaining photoresistor is removed and accordingly only the anode 4 remains on the surface of the glass substrate 1.
The above-described process is illustrated in the sequence shown from FIG. 2(A) to 2(E).
When a glass paste is printed successively from 7 to 10 times and dried in the spaces between the anodes 4 after removal with the photoresist 6 according to aforementioned process, the barrier ribs 2 are formed as shown in FIG. 2(F).
As described above, according to the conventional screen printing method for forming the barrier ribs, the glass paste is printed between the anodes 4 that have been formed with a predetermined pattern on the glass substrate 1. However, at this moment, since the glass is printed after removing the photoresist 6 remaining on the surface of said anode 4, owing to the discordance of the anode 4 located on the glass substrate 1 and the openings 9 of the printing mask 8 fixed at the mask frame 7, various problems arise as described below.
That is to say, in those cases when the barrier ribs are formed by using the conventional barrier rib forming method, and since the anode 4 formed on the surface of the glass substrate 1 is coated with a transparent ITO film, there has been a problem wherein it is hard to correctly print the glass paste by aligning the barrier rib forming portion between the anode 4 with said openings 9 of the printing mask 8.
That is, when the glass substrate 1, formed with the ITO pattern, and the printing mask 8 are positioned with one another and when viewing the glass substrate 1 through the openings 9 of the printing mask 8, and since the ITO film is transparent, it is difficult to discriminate that the opening 9 and the ITO pattern on the surface of the glass substrate are overlapped with error.
Therefore, when the glass paste is printed in a state that the openings 9 and the ITO pattern are overlapped with some error, since the glass paste is printed on a part of the surface of the ITO pattern, the area of the anode is reduced. Accordingly, the discharging property of the display element becomes deteriorated.
Further, in those cases when the glass paste is printed with the thickness of several .mu.m on the slippery glass substrate, a phenomenon wherein the glass paste spreads laterally has arisen. Spreading on the glass substrate between the anodes occurs with a ITO of the thickness of several thousand A. Accordingly, the essential area of the anode becomes decreased, and consequently the deterioration of the discharging characteristic and the luminance occurs.